2.2.6 Component Technologies

This segment of the program is dedicated to the development of component technologies which have been determined to be of potential benefit in addressing multiple needs of the known robotics requirements. These elements of the program are typically long lead-time items, which may take many years to fully develop and bring to an appropriate level of readiness. However, if successfully completed, these elements typically have the potential of significantly improving or even revolutionizing the state-of-the-art in space telerobotics technology. This portion of the current program includes such elements as fundamentally new robotic joint designs, exoskeleton systems, microtelerobots, and widely-applicable proximity sensor technology. The long term goal of this effort is to develop a series of component technologies which can then be incorporated into larger robot assemblies and full application systems. This effort is phased such that technology components "spin-off" from the component development level to the next level on a regular basis. It is anticipated that this area will continue throughout the life of the program, producing an increasingly-beneficial series of fundamental technologies.

Multiple Interacting Robots

Vision and Touch Guided Grasping

Redundant Robot Systems

Robotics Control Technology

Multiple Interacting Robots

The Aerospace Robotics Laboratory (ARL) at Stanford University is pursuing two fields of research as discussed below:

Control of Free-Flying Space Robot Systems

This research area is dedicated to the development of Free-Flying Space Robots that can be directed at an intuitive, task level to perform typical space operations. There are three prototype space robot vehicles employed for experimentation, and there are two major focus areas of these experiments. The first area is concerned with upgrading the FFSR's toward operational systems. This includes incremental modification our present FFSR design to incorporate various 3D capabilities and development of human-interface/robot-control techniques for greater functionality in unstructured environments. The second area of research is concerned with expanding the basic set of tasks that the FFSR's can perform (such as "capture", "move", "dock", etc.), and to increase the reliability of the current set of task capabilities through the development of new control techniques.

Focus and Directions:

FY 94 Demonstrate neural network-based thruster map system, capable of identifying thruster misalignment or failure and adaptively adjusting controller to compensate.

FY 95 Perform autonomous robot-satellite rendezvous using the Global Position System (GPS) as the primary navigation sensor. The capability demonstrated by this experiment can be directly applied to future on-orbit free-flying robot servicers as a high-precision navigation and rendezvous control system.

FY 95 Assemble structures using a team of Free-Flying Space Robots. This experiment will be a test of new robotic control theory for complex dynamic systems, and will enable multi-DOF robot-manipulator systems to autonomously perform precise position and force control in highly dynamic environments, such as space.

FY 96 Identify, track, and manipulate objects that the robot has no prior knowledge, using the human controller to perform initial object recognition and identification tasks. This capability will enable robots to effectively sense and manipulate objects in unstructured environments, while the human directs tasks to be performed on the object at a high level.

High Performance Control of Flexible Manipulators

This area of the research pursues general theoretical advances in automatic control theory that can be applied to a variety of robotic and other dynamic systems. In order to refine and transfer these theories to operational systems, all of the results are experimentally verified. This research is primarily conducted on three hardware platforms: a Single Link Flexible Manipulator with complex dynamic payloads, a two-link Flexible Drive Train Manipulator with a mini-manipulator at the end effector, and a Dual Two-DOF Cooperating Arms robot used to perform assembly of objects that are both rigid and compliant. There are four major thrusts of this research: Adaptive Control of Manipulators with Complex Dynamic Payloads, Cooperative Assembly of a Flexible Parts Under Task Level Control, Optical Tracking of Objects using an Arm Mounted Camera, and Manipulation of Objects in the Environment by a Flexible Macro-Mini Manipulator

Focus and Directions:

FY 93 Developed and experimentally verified optimal control techniques in conjunction with flexible mode modeling to control a two-link flexible manipulator equipped with a mini-manipulator. These techniques showed order-of-magnitude increase in speed for positioning the end-effector of a flexible robot arm.

FY 94 Demonstrated control techniques for cooperative robotic assembly of flexible parts. This new capability expands the range of objects that autonomous robots can reliably assemble.

FY 94 Track an object or a line in real time using a macro-mini manipulator equipped with a wrist-mounted camera. This capability can be applied to automate various surface inspection routines.

FY 95 Demonstrate adaptive control for manipulation of payloads that possess significant internal dynamics. An example application is the shuttle RMS manipulating a satellite that contains fuel or has flexible appendages.

FY 96 Use a flexible macro-mini robot arm to capture and manipulate a rigid object using position, force, and object impedance control. This work is intended to resolve several fundamental control issues that are of concern to attached servicer robots currently under development.

Point of Contact:
Robert Cannon
(415) 723-3602
cannon@sun-valley.stanford.edu

Vision and Touch Guided Grasping

This task conducts fundamental research and demonstrations in the mutually complementary areas of real-time vision and touch sensing, robust grasping mechanisms, and computer-based grasp control. It enables autonomous and semi-autonomous grasping tasks in space of human-fabricated objects (e.g., tools) and natural objects (e.g., loose rocks) covering a wide range of object size and geometry. The task will conduct experimental demonstration of how to acquire and grasp stationary spherical objects and cylindrical objects using coordinated robotic vision and control algorithms. It will conduct experimental evaluation of how to use force and torque feedback to improve the grasping operations. It will analyze sensitivity of robotic grasp system performance to object size and geometric features and address appropriate end-effector design. The research will be targetted to planned and on-going missions utilizing earth-orbiting and planetary surface robotics. The task will be performed at the Massachusetts Institute of Technology and will support the research of Dr. J. Kenneth Salisbury, Prof. Jean-Jacques E. Slotine, graduate students, and research staff.

Focus and Directions:

FY94 Vision and touch guided grasping experiments.

FY95 Loose rock grasping evaluation and experimentation.

FY96 Object dynamics adaptive configuration experiments.

FY97 On-line assessment of grasp feasibility.

FY98 Field experiments in simulated space scenarios.

In FT 1995, this task was incorporated into the Remote Geologist task.

Point of Contact:
Ken Salsbury
(617) 253-5834
jks@ai.mit.edu

Redundant Robot Systems

The objectives of this program element are to perform research in advanced robotics regarding fault tolerant manipulator systems. For space operations, extraordinary reliability will be needed to protect space assets, and to ensure that robots are capable of physical task performance over long duration missions. The goal of the failure tolerance in manipulator design task is to develop a major tested to treat failure tolerance in mechanical structures associated with robotics and computer controlled machines. Three levels of failure tolerance in the mechanical structure and similar controlling software will be developed based on criteria-based decision making in a finite fault tree to operate the system to avoid faults in real time. This work is being conducted at the University of Texas at Austin (UT), under the sponsorship of the Johnson Space Center.

Focus and directions:

FY94 Test fault tolerant, dual actuator module for backlash, stiffness, friction, etc.

FY94 Develop an advanced criteria for resource allocation in systems with redundancy.

FY94 Complete design and fabrication of prototype two dof, fault tolerant knuckle module.

FY95 Redesign fault toleratnt actuator module for improved performance based on previous year testing.

FY95 Perform characterization testing of fault tolerant, two dof knuckle.

FY95 Develop level III and level IV fault tolerance of the 17 dof RRC system.

FY95 Complete real time algorithms for Level III fault tolerance including collision avoidance and generalized inverses.

Point of Contact:
Del Tesar
(512) 471-3039
:tesar@mex.cc.utexas.edu

Robotics Control Technology

This project supports technology development for International Space Station Alpha (ISSA) robotic system development by: (1) providing a realistic hardware testbed for the evaluation of ISSA dexterous manipulator tasks, and (2) developing and demonstrating advanced telerobotic technologies which support these tasks. The ISSA program is predicated on the use of Orbit Replaceable Units (ORUs) for station and system maintenance. With limited crew resources available and a need to minimize hazardous EVA operations, the changeout of the ORUs with automated dexterous manipulators is a critical capability which has not been studied in detail. Thorough and early ground testing of the ORU and end effector hardware is essential to verify the feasibility of dexterous manipulator ORU manipulation and to potentially impact the manipulator design since there is no in-space experience with dexterous manipulators and no on-orbit test program currently planned. In conjunction with the hardware tests, a detailed evaluation of the ORU changeout task scenarios is needed to verify their validity. This evaluation will also identify areas where advanced technologies can make the operator's task easier and/or more reliable. Potential robotic technologies include force/moment accommodation, machine/computer vision control, 7-DOF control (redundancy management), and collision avoidance and detection.

The program will be conducted in close coordination with the ISSA Boeing/Oceaneering robotics team. System requirements, specifications, task scenarios, and hardware details will be solicited from the ISSA program and implemented in a hardware testbed. Specific tasks and analyses may also be performed at the request of the ISSA office. Results of this early hardware testing can be applied to the design of the ISSA dexterous manipulator system, the ORU interface design, and the ORU changeout task scenarios. In addition to advanced technology development for ISSA, the testbed will directly support ongoing ISSA dexterous manipulator system design review activities.

Approach:

The program will be conducted in the Dexterous Manipulator Test Bed (DMTB), a full scale hardware test facility configured to represent an ISSA dexterous manipulator and ORU changeout environment. The DMTB includes a seven degree-of-freedom hydraulic manipulator arm and an end effector designed to grasp the ORUs' special robotic handles. Video cameras and artificial lighting are provided to assist the operator in the ORU changeout task. The dexterous manipulator is currently controlled from a mockup of the Space Shuttle's aft flight deck, but work is underway to develop an ISSA telerobotic workstation mockup. The DMTB will incorporate realistic ORU hardware to provide an early evaluation of hardware mechanisms, operator procedures, and camera/lighting locations.

The test program will address concerns with the ISSA dexterous manipulation tasks identified by Oceaneering Space Systems in a Robotics Technology Study prepared for the ISSA Program Office and the Code X Telerobotics Program. Initial testing will be concerned with ORU alignment and viewing needs and will determine the video coverage and passive alignment required for ORU tasks. These tests will also evaluate the operation of end effector and ORU interface hardware mechanisms in detail. The adequacy and consistency of operator procedures specified to perform the ORU tasks will also be established. Hardware mechanism problems experienced during these tests will be used to develop error recovery procedures.

Realistic simulation of the ORU task operations will provide an accurate identification of areas where more sophisticated systems could make the operator's task easier. Candidate systems include force/torque accommodation to aid the operator in aligning the manipulator with the ORU, machine vision to guide the manipulator arm, and special sensors or a world model knowledge base to keep the manipulator arm from colliding with objects in its workspace. A high fidelity graphical and control simulation environment is also required for a meaningful evaluation of advanced systems. The goal of this effort is to make the operator's task easier, to make the task performance more reliable, to increase operator productivity, and to reduce operator workload

Focus and Directions:

Dec 94 Define testbed baseline specifications

May 95 Complete video coverage/artificial lighting tests

July 95 Complete end effector mechanism/ORU interface tests; this will include an assessment of task sequences and operator procedures

Sept 95 Complete force/moment accommodation system evaluation

Point of Contact:
Wallace Harrison
(804) 864-6680
j.e.pennington@larc.nasa.gov